In most of current object tracking and prediction methods based on real-time videos, a possible area in which an object may appear in a next frame is predicted using a Kalman filter based on an object tracking result of a current frame. When the next frame is played, the object is searched in the predicted area of the next frame. By using the prediction result of a previous frame, the searching area of the current frame is reduced. Therefore, the amount of calculation is significantly reduced, and the tracking speed is accelerated, improving real-time object tracking.
FIG. 1 illustrates a schematic diagram of three-dimensional (3D) display apparatus. As shown in FIG. 1, the 3D display apparatus includes a head tracker 102, a tracking module 104, a display module 106, and a controllable optical system 108. The tracking module 104 may further include a calculation module 104-2 and a control module 104-4.
The head tracker 102 may be configured to track a position of a user's head. The tracking module 104 may be configured to perform calculation and control the display module 106 and the controllable optical system 108 based on the position of the user's head obtained by the head tracker 102, such that a correct image can be displayed to the user. The display module 106 may be configured to display the image under the control of the control module 104-4. The controllable optical system 108 may be configured to perform adjustment under the control of the control module 104-4, such that the correct display can be provided to the user.
FIG. 2 illustrates a schematic diagram of an object tracking sensor sampling raw data of an object at time t0. As shown in FIG. 2, an object that is tracked may be a left eye and a right eye of a user. The tracked object may also be a head, a face or other parts of the user.
However, in the object tracking process based on a real-time video, an infrared detection device, a depth camera, or a wearable device, etc., due to irresistible factors (e.g., the calculation time), when the user is moving fast, a position tracking result of the tracked object obtained by a current tracking algorithm may have a certain spatial delay. FIG. 3 illustrates a schematic diagram of motion of a user during a time period Δt of a tracking algorithm. As shown in FIG. 3, when the raw data is calculated by the current tracking algorithm in a time period Δt, the user continues to move. Therefore, there is a certain spatial delay for the object tracking result. If this object tracking result is applied to autostereoscopic 3D displays, the 3D display effect may be affected, for example, reverse visual phenomena may happen when a person moves fast.
FIG. 4 illustrates a schematic diagram of a reverse visual phenomena happened when the spatial delay is not compensated. As shown in FIG. 4, at time t0, an object (e.g., eyes) is located at position coordinates (x0, y0, z0). At this point, a camera captures an image of a user, or a sensor (e.g., an infrared sensor, a depth sensor, and so on) collects data of the tracked object, thereby obtaining raw images/data. A series of analysis and processing operations are performed using an existing tracking algorithm. At time t0+Δt, position coordinates (x0, y0, z0) of the tracked object are reported (it is assumed that the correct position of the tracked object can always be accurately calculated using the current tracking algorithm). Based on the obtained position coordinates of the tracked object, a corresponding 3D image is displayed on a display apparatus, where a left eye viewing area and a right eye viewing area of the user correspond respectively to the positions of the left eye and the right eye of the user calculated by the tracking algorithm. During this process, time consumption for processing the tracking algorithm and the arrangement algorithm is Δt. The display apparatus includes a display module and a light-splitting device, where the light-splitting device is configured to send the image displayed on the display module respectively to the left eye and the right eye of the user, such that the 3D image is displayed.
In fact, because the user may continue moving in the time period Δt, an actual position of the tracked object is changed at time t0+Δt. Therefore, the actual position of the tracked object is not at the position coordinates (x0, y0, z0), whereas the actual position of the tracked object moves to position coordinates (x′, y′, z′) at time t0+Δt. Due to the irresistible factors (e.g., the calculation time), the position calculated by using the current tracking algorithm has a time delay Δt. The difference between the calculated position and the actual position is determined by Δt and the moving speed of the tracked object. In this case, if no compensation for the spatial delay of the tracked object is performed during an image arrangement of the 3D display, reverse visual phenomena may happen. That is, the left eye of the user is actually located at the right eye viewing area of the 3D stereo display, and the right eye of the user is actually located at the left eye viewing area of the 3D stereo display, thereby presenting an erroneous display effect.
The disclosed methods and apparatuses are directed to solve one or more problems set forth above and other problems. For example, the disclosed methods and apparatuses can provide technical solutions for tracking a moving object in both a two-dimensional (2D) plane and a three-dimensional (3D) space, improving data accuracy of object tracking.